The present invention relates to an image reader capable of reading an image with an image sensor for converting a read image into an electric video signal and transferring a video signal obtained by digitizing the electric video signal with an A/D converter to an external unit and its control method and an image read method.
An image reader (hereafter referred to as image scanner) has been known so far, which reads a manuscript with an image sensor to convert it into an electric video signal and moreover, converts the analog signal into a digital signal with an A/D converter to transfer it to an external unit.
This type of the image scanner has a home-position sensor (hereafter referred to as HP sensor) for detecting the position of an image sensor in accordance with on/off of the output of a photodiode or the like when moving the image sensor for scanning a manuscript to a read start position (hereafter referred to as home position) in order to determine an image read start position and determines the read start position with the home position sensor.
Moreover, a product has been recently marketed which detects a home position (hereafter referred to as HP detection) without using the above photodiode in order to cut down the cost of a scanner. In the case of this type of the product, a specific pattern is set to the read start position of a scanner to decide a reference position by detecting the pattern.
For example, a white plate and a black plate are arranged out of an image region adjacently to each other and the region is read by an image sensor to detect the boundary between the white plate and the black plate in accordance with the output of the image sensor and perform HP detection.
Moreover, it is also performed to combine detection of the above pattern with a HP sensor, move an image sensor up to the position of the HP sensor, and then detect the boundary between a white plate and a black plate.
However, the above detection methods have the following problems.
(1) The gap between a pressure plate and a housing (a body of a scanner)may be erroneously detected as the boundary between a white plate and a black plate.
(2) Because external light comes in from the gap between a pressure plate and a housing, the boundary between a white plate and a black plate is not accurately detected.
(3) When using a HP sensor, HP detection cannot be made if the HP sensor is damaged or external light enters the read region of an image scanner.
(4) By using a complex pattern as a specific pattern, accurate HP detection can be made. However, when using an inexpensive scanner, it is necessary to perform HP detection only from a simple black region in order to further cut down the cost before setting a complex pattern. However, the processing section (CPU) for performing the detection frequently has a low performance and therefore, it is difficult to decide whether pattern data values are matched each other at a high speed.
Moreover, it is limited to perform complex processing. Therefore, erroneous detection may occur depending on the manuscript on a manuscript table and an image sensor may stop at a position other than a reference position.
The present invention is made to solve the above problems and its object is to provide an image scanner for performing HP detection by detecting the boundary between a white plate and a black plate without erroneously detecting the boundary between a pressure plate and a housing as the boundary between the white plate and the black plate. It is another object of the present invention to provide a method for controlling an image scanner for performing HP detection by detecting the boundary between a white plate and a black plate, capable of reducing a scan time.
It is still another object of the present invention to provide an image scanner for performing HP detection by detecting the boundary between a white plate and a black plate, capable of accurately performing HP detection without being influenced by external light incoming from the gap between a pressure plate and a housing.
It is still another object of the present invention to provide a method for controlling an image scanner capable of accurately performing HP detection even when intensities of external light are changed by operator""s setting a read range of an image sensor through an external unit.
It is still another object of the present invention to provide a method for controlling an image scanner capable of accurately performing HP detection even if a HP sensor is damaged or external light enters a read region of an image scanner.
That is, according to the first aspect of the present invention, it is possible to obtain a method for controlling an image scanner for reading an image from an image read region by scanning the region with an image sensor in a predetermined direction and having transfer means for transferring a video signal to an external unit and a white portion and a black portion which can be read by the image sensor and which are formed out of the image read region; wherein
the steps of obtaining a video signal converted by the image sensor again at a position a predetermined distance separated smaller than the width of the predetermined direction of the black portion with the image sensor and deciding whether a black decision level is continuously satisfied when the level of the video signal is equal to a level satisfying the black decision level for deciding a predetermined-density black color are included to detect the read reference position of the image sensor by detecting the boundary between the white portion and the black portion with the image sensor.
Moreover, according to the second aspect of the present invention, it is possible to obtain a storage medium storing a program for detecting the boundary between a white portion and a black portion formed out of an image read region in which data can be read by an image sensor in an image scanner for reading an image from the image read region by scanning the region with the image sensor in a predetermined direction, wherein a program is stored which includes the steps of obtaining a video signal converted by the image sensor again at a position a predetermined distance separated smaller than the width of the predetermined direction of the black portion with the image sensor and deciding whether a black decision level is continuously satisfied when the level of the video signal is equal to a level satisfying the black decision level for deciding a predetermined-density black color in order to detect the read reference position of the image sensor by detecting the boundary between the white portion and the black portion with the image sensor.
Furthermore, according to the third aspect of the present invention, it is possible to obtain a method for controlling an image scanner having an image sensor for converting a read image into an electric video signal, transfer means for transferring the video signal to an external unit, and a white portion and a black portion out of an image read region; wherein
the read range of the image sensor in the main scanning direction is made different from an image read range when detecting a reference position of the image sensor by detecting the boundary between the white portion and the black portion with the image sensor.
Furthermore, according to the fourth aspect of the present invention, it is possible to obtain a storage medium storing a program for detecting the boundary between a white portion and a black portion formed out of a region in which data can be read by an image sensor in a image scanner for reading an image from an image read region by scanning the region with the image sensor in a predetermined direction; wherein
a program is stored which includes the step of making the read range of the image sensor in the main scanning direction different from an image read range when detecting the read reference position of the image sensor by detecting the boundary between the white portion and the black portion with the image sensor.
Furthermore, according to the fifth aspect of the present invention, it is possible to obtain a method for controlling an image scanner having an image sensor for converting a read image into an electric video signal, transfer means for transferring the video signal to an external unit, and a white portion and a black portion out of an image read region, wherein
the black level of an output of the image sensor is set before detecting a read reference position of the image sensor in order to detect the reference position by detecting the white portion and the black portion with the image sensor.
Furthermore, according to the sixth aspect of the present invention, it is possible to obtain a storage medium storing a program for controlling an image scanner having an image sensor for converting a read image into an electric video signal, transfer means for transferring the video signal to an external unit, and a white portion and a black portion out of an image read region; wherein a program is stored which includes the step of setting the black level of the output of the image sensor before detecting a read reference position of the image sensor in order to detect the reference position by detecting the boundary between the white portion and the black portion with the image sensor.
Furthermore, according to the seventh aspect of the present invention, it is possible to obtain an image scanner for reading images from a manuscript every line by transferring an image sensor in the vertical-scanning direction, which comprises detection means for detecting a predetermined pattern for the image sensor to read an image, control means for determining the reference position of the image sensor to make the image sensor start reading an image in accordance with the detected pattern, and storage means for storing the detected pattern and the determined reference position, wherein initialization movement of the image sensor before image read when a power supply is turned on is performed in accordance with the reference position determined by the detected pattern in the vertical-scanning direction and movement of the image sensor after image read is performed in accordance with a reference position read out of the storage means.
Furthermore, according to the eighth aspect of the present invention, it is possible to obtain an image read method for reading images from a manuscript every line by transferring an image sensor in the vertical-scanning direction, which comprises the steps of detecting a predetermined pattern provided for the image sensor to read an image, determining the reference position of the image sensor in accordance with the detected pattern to make the image sensor start reading an image, storing the detected pattern and determined reference position in storage means, performing the initialization movement of the image sensor before image read when a power supply is turned on in accordance with the reference position determined by the pattern detected in the vertical-scanning direction, and performing the movement of the image sensor after image read in accordance with the reference position read out of the storage means.
Furthermore, according to the ninth aspect of the present invention, it is possible to obtain a storage medium storing a program for reading images from a manuscript every line by transferring an image sensor in the vertical-scanning direction, wherein a program is stored which detects a predetermined pattern for the image sensor to read an image, determines the reference position of the image sensor in accordance with the detected pattern to make the image sensor start reading an image, stores the detected pattern and determined reference position in storage means, performs the initialization movement of the image sensor before image read when a power supply is turned on in accordance with the reference position determined by the detected pattern in the vertical-scanning direction, and performs the movement of the image sensor after image read in accordance with the reference position read out of the storage means.